As a result of the expanding use of rare earth-bearing materials in modern technology, such as, for example, in the form of rare earth-iron alloy magnetostrictive transducers, delay lines, variable frequency resonators and filters and rare earth-iron-boron alloy permanent magnets, the cost and environmental problems associated with their waste and scrap disposal have become an increasing concern. Additionally, the high cost of rare earth metals makes simple disposal of rare earth-bearing waste or scrap materials economically unattractive. Up to the present time, there have been no large scale operations to recover rare earth metals from scrap and waste materials.
One attempt at recovering rare earth metals from waste and scrap involves dissolution of the waste/scrap material in acid media followed by precipitation of a rare earth compound. The rare earth compound is converted to a rare earth trifluoride which is then reduced to rare earth metal by calcium reduction. U.S. Pat. No. 5,129,945 describes a recovery process of this type. Although the recovery process is effective, it is time consuming and requires the use of expensive non-recoverable reagents.
Another more recent attempt at recovering rare earth metals from rare earth-transition metal materials has produced a process that promises to be less costly and more adaptable to a variety of scrap materials. This process is based on liquid-liquid or liquid-solid extraction technology depending upon the specific rare earth alloy scrap being processed. The process allows rare earth recovery without the expensive and time consuming acid digestion and fluoride reduction steps employed in the recovery process described in the preceding paragraph. Rare earth metals are recovered in this process using reagents which are essentially completely recycled. Thus, the waste stream is kept to a minimum. U.S. Pat. No. 5,238,489 describes a recovery process employing a combination of leaching and flotation to separate different rare earth scrap alloys in a scrap mixture from one another.
An object of the invention is to provide a liquid metal extraction process for recovering one or more rare earth metals from rare earth metal-bearing waste, scrap and other material in order to recover the rare earth metal component for reuse.
Another object of the invention is to provide a liquid metal extraction process for recovering one or more rare earth metals from rare earth metal-bearing waste, scrap and other material in a manner to recycle the liquid metal extractant in the recovery process.